Electrical switching assembly

ABSTRACT

The invention relates to switching apparatus having a pair of input terminals (102, 104) and 2 P  pairs of output terminals (106a, 106b). The switch comprises p rows of switches K i ,j with the ith row having 2 i  unit switches. It also comprises a control circuit (108) which enables the state of all the switches in a given row to be controlled together, thereby enabling the pair of input terminals to be connected to any pair of output terminals.

The present invention relates to an electrical switching assembly.

More precisely, the invention relates to controllable apparatus enablinga pair of input terminals to the switching apparatus to be selectivelyconnected to any one of n pairs of output terminals of the switchingapparatus.

There exist numerous occasions on which it is useful to have such anelectrical switching assembly available. This applies in particular forautomatic electrical test apparatus for determining and verifying theelectrical transmission properties between various electrical componentswhich are connected to a main line via branch lines coupled to the mainline by couplers. A certain number of electrical installations are to befound having various electronic or electrical components, in particularas constituted by sensors or actuators, that interchange data via asingle main line, with this type of connection usually being called a"bus" or a "harness/bus". This disposition is to be found, inparticular, in electrical circuits of the kind installed, for example,in space rockets for interconnecting the various sensors or actuators ofthe rocket. Given the cost of such a rocket and of launching it, it isclearly of great importance for the electrical connection membersbetween its various components to be capable of being fully tested priorto being installed in the rocket or in any similar installation in orderto avoid risks of breakdown or faulty operation.

In the special case of space installations, this type of "harness/bus"interconnection must satisfy the standard: MIL-STD-1553B. However, forother types of installation, it is necessary to verify thatinterconnections comply with standards of the same type.

In general, the various interconnection systems must be tested indifferent configurations, i.e., in succession, when each of thecomponents connected by branch lines behaves as a sender, when itbehaves as a receiver, when an input load is applied thereto to simulatea card, i.e. an electronic circuit, and possibly when one of thereceivers or senders referred to below as a "subscriber" is shortcircuit or open circuit to simulate damage to the installation as awhole in order to test its behavior in such a configuration.

It will easily be understood that when the harness/bus is used tointerconnect a large number of components, e.g. about ten, the number ofdifferent configurations to be tested in order to be sure that eachbranch line is properly coupled to the main line is extremely high.

With the means used at present, which are means that are essentiallymanual and not automatic, the time that would be required for testingall configurations properly becomes prohibitive. Consequently, only alimited number of critical configurations are actually tested. It willbe understood, that although such a test procedure is statisticallycapable of detecting breakdowns or damage of the kind that is the mostfrequent, it is incapable of ensuring that the interconnectioninstallation will operate properly in all of its possibleconfigurations.

As already briefly outlined, when this system of interconnections andthe quality of its operation are critical points for the operation of arocket or similar equipment where cost is very high, it is advantageousto ascertain in as complete a manner as possible that all of theelectrical lines are operating properly before mounting the system inthe rocket.

It will also be understood that such an electrical test installation iscompletely under the control of computer means. It is thus veryimportant for the switching assembly to be convenient for control bycomputer instructions.

Finally, it can be seen that in order to obtain measurements that arevery accurate and repetitive, it is important for the architecture ofthe switching assembly to avoid introducing interfering effects, andthat it must not introduce variations in electrical characteristicsdepending on the particular electrical path defined through the switchfor connecting the pair of input terminals to one of the m pairs ofoutput terminals.

To achieve this object, according to the invention, the electricalswitching assembly is characterized in that it comprises:

two external terminals forming said input of said switching assembly;

p rows of switches, row i having 2^(i) switches, each switch having aninput terminal, first and second output terminals, and controllableelectrical connection means for selectively connecting said inputterminal to said first output terminal or to said second outputterminal, each of said first and second output terminals of switches inrow i being electrically connected to the input terminal of a respectiveswitch in row i+1, the two external terminals being connected torespective input terminals of the two switches of the first row; and

control means for controlling the controllable electrical connectionmeans of all of the switches in the same row simultaneously in such amanner that for all of the switches of the same row, the input terminalis connected to the first output terminal or is connected to the secondoutput terminal depending on binary control states;

each of the 2^(P) first output terminals and each of the 2^(P) secondoutput terminals being connected to a respective one of the switchinginput or output terminals, and the first and second output terminals ofthe ith row being connected to the input terminals of the switches ofthe row in such a manner that for each combination of binary controlstates of the control means of the rows of switches, the two externalterminals of said switching assembly can be connected to any one singlepair of switching input or output terminals.

It will be understood that the switching assembly is constituted by abinary tree structure of sets of switches organized in rows. The statesof the switches belonging to a given row are changed simultaneously andthe ON state for each switch line enables the terminals external to theswitching assembly to be electrically connected to a single pair ofswitching outlet or inlet terminals, said pairs of terminals themselvesbeing connected to the branch line state circuits, i.e. to the"subscriber" cards. This tree structure makes it possible to simplifycontrol of the switching assembly while still enabling the externalinput terminals to be connected in unique manner to the switching outputterminals. This disposition also serves to shorten line length.

Other characteristics and advantages of the present invention appearmore clearly on reading the following description of a preferredembodiment of the invention, given by way of non-limiting example. Thedescription refers to the accompanying figures, in which:

FIG. 1 is a diagram showing a switching assembly of the invention;

FIG. 2 is a block diagram of the electrical test apparatus a whole;

FIG. 3 is a diagram showing the switching assembly in send mode togetherwith a "subscriber" card; and

FIG. 4 is a view similar to FIG. 3, but showing the switching assemblyin receive mode.

A preferred embodiment of a switching assembly is described initiallywith reference to FIG. 1.

The switching assembly 100 essentially comprises p rows of unit switchesgiven generic reference K. The first row of switches is constituted bytwo unit switches K₁,1 and K₁,2 whose inputs are given generic referencea and are connected to respective input terminals 102 and 104 of theswitching assembly. In generic manner, each switch K_(i),j has twooutput terminals given respective references b and c. The second row ofthe switch has four unit switches that are thus referenced K₂,1 to K₂,4.Each first output terminal b of a switch in row i is connected to theinput terminal a of a respective switch in row i+1, and each outputterminal c of a switch in row i is connected to the input a of adifferent respective switch in line i+1. A switch tree structure is thusobtained, with each row i having twice as many switches as row i-1. Moregenerally, row i of unit switches K_(i),j has 2^(i) switches. In theexample under consideration, the switching assembly has four rows ofunit switches, which means that the fourth row has 2⁴ unit switchesreferenced K₄,1 to K₄,16. The outputs b and c of the unit switches K ofthe last row are respectively connected to positive external outputterminals 106a of the switching assembly and to negative terminals 106bof the switching assembly.

As can also be seen in FIG. 1, the switch has a control unit 108 havingas many control outputs 110 as there are lines of unit switches, i.e.four in the example under consideration. Each output 110 of the controlapparatus 108 serves to cause the inputs a of the unit switches in thesame row to be connected simultaneously to the output terminals b orsimultaneously to the output terminals c. A full control instruction forthe switch 100 thus comprises four binary digits indicating whether theunit switches K of a row i should be in a position that connects theirinputs a to their terminals c or in a position that connects theirinputs a to their terminals b.

The electrical connections between the outputs b and c of the unitswitches K_(i) of row i and the terminals a of the switches K_(i+1) ofrow i+1 are such that the inputs 102 & 104 of the switching assembly canbe connected to any one of the pairs of external output terminals of theswitch 106a & 106b, and to one pair only. FIG. 1 shows a possibleconfiguration for said electrical connections.

In other words, when a control signal is applied to the control input108a of the control apparatus 108 of the switch 100, the unit switchesof the various rows take up a state enabling the input 102 & 104 to beconnected to the selected pair of external output terminals 106a & 106b.

The unit double-pole switches K can be of any kind. Similarly, themoving contact control means of the switches which are represented inFIG. 1 merely by dashed lines can be of any kind. In particular, it ispossible to use relays whose states are controlled by means ofopto-couplers.

The tree structure of the switching assembly 100 presents numerousadvantages. Switching control is simplified since it suffices to providep binary digits to connect the external terminals connected to thesignal generator or to the measuring device to a selected one of the2^(P) pairs of terminals connected to the "subscriber" cards. Also, eachelectrical path defined between the input pair of terminals and any oneof the output terminals has the same number of intermediate contacts,thereby ensuring the same electrical conduction qualities regardless ofpath, with the path lengths also being all substantially equal. Inaddition, for each position of the unit switches, they define only twoelectrical paths that do indeed extend from the input terminals to onepair of output terminals, and no partial paths are defined as seen fromthe input terminals, thereby avoiding interfering phenomena which couldbe induced by partial paths connected to the input terminals.

An entire apparatus for electrically testing the harness/bus and makinguse of the switch of FIG. 1 is described below with reference to FIG. 2.

In FIG. 2, a bus 10 to be tested is shown connected to the testapparatus 12. The bus 10 is constituted by a main line 14 having nbranch lines 16 connected thereto. Each branch line 16 is connected tothe main line 14 by an electrical coupler 18.

The electrical test apparatus is essentially constituted by a controlunit 20 for applying and controlling the battery of tests to which thebus 10 is to be subjected, an electrical measuring device 22 such as anoscilloscope or a recorder, a controllable electrical signal generator24, first and second electrical switches respectively referenced 26 and28, and m branch line state circuits given overall reference andreferred to below for simplification purposes as "subscriber" cards.

The switches 26 and 28 have the architecture described with reference toFIG. 1.

The control unit 20 essentially comprises a computer machine 32associated with a program memory 34 which enables the variousconfigurations of tests to be applied to the bus 10 to be run. Thecomputer apparatus 32 is preferably associated with means 36 for displaypurposes and for printing results. The computer control apparatus 32 isalso coupled to a converter 38 which serves to convert the instructionsissued by the computer apparatus 32 into executable control signalsenabling the states of the various components of the test apparatus 12to be controlled. The computer control apparatus 32 is also connected tothe control input 24a of the electrical signal generator 24 in order todefine the form of the electrical signal which is to be applied for thetest stage under consideration.

More precisely, as shown in FIG. 2, each branch line 16 of the bus 10 isconnected to the input and/or the output of a "subscriber" card 30. Each"subscriber" card 30 is connected to an output 40 of the first switch 26and to an input 42 of the second switch 28. The input 44 of the switch26 is connected to the output of the electrical signal generator 24,while the output 46 of the second switch 28 is connected to the input ofthe electrical measuring apparatus 22. The converter 38 has a firstoutput 48 which is connected to the control input 28a of the switch 28and a second control output 50 which is connected to the control input26a of the first switch 26.

As explained in greater detail below with reference to FIGS. 3 and 4,the switch 26 enables its input 44 to be connected to one of the outputs40 of said switch and thus to one of the m "subscriber" cards 30.Similarly, the switch 28 serves to connect one of its inputs 42, i.e.one of the "subscriber" cards 30, to its own output 46, i.e. to themeasuring device 22. The conversion apparatus 38 includes a thirdcontrol output 52 which is applied to the control input 30a of each ofthe "subscriber" cards 30. The converter can use its output 52 to applya control signal to each "subscriber" card serving, as explained ingreater detail below, to define the state of each of the branch lines 16during a test stage. Depending on which control signal is applied to theinputs 30a of the "subscriber" cards 30. Each subscriber card canconnect the branch line with which it is associated to the electricalsignal generator 24 or to the measuring device 22, or to neither ofthem. Under such circumstances, the control signal can put the"subscriber" card in a state that corresponds to short circuiting thecorresponding branch line 16 or that represents the nominal operatingload applied thereto.

The way in which the electrical test apparatus 12 of FIGS. 2 to 4operates is described below. For each step in a series of tests, onebranch line sends, one branch line receives, and the other branch linesare either short circuited to simulate a breakdown, or open circuit, orelse connected to their normal loads. Implementing the test step thusconsists in the program 34 defining the number of the sending branchline 16, the number of the receiving branch line 16, and the state ofeach of the other branch lines. It is also necessary to define dataspecifying the characteristics of the signal that is to be sent by thesending branch line and possibly also the nature of the measurements tobe performed.

These various items of information are transmitted to the converter 38which serves firstly to control the various "subscriber" cards 30 as afunction of the state of the branch line associated therewith. Moreprecisely, one of the "subscriber" cards is controlled to connect thebranch line to the electrical signal generator 24 and another card iscontrolled to connect the "subscriber" card to the measuring device 22.The other "subscriber" cards are controlled to take up respective onesof the other possible states. Simultaneously, the converter 38 controlsthe switches 26 and 28 so that the sending "subscriber" card is indeedconnected to the generator 24 and so that the receiving "subscriber"card is indeed connected to the measuring device 22. In addition, theelectrical signal generator 24 is controlled to apply the desired formof electrical signal for the test. Once these various connections havebeen set up, the measuring device 22 performs the measurements ofelectrical characteristics as specified in the test, which measurementsare transmitted to the computer apparatus 32 which enables them to beprocessed and possibly displayed on the display apparatus 36 or on apaper medium, or else to be stored on a computer medium.

It will be understood that the general organization of the testapparatus makes it possible in a relatively short length of time tocause each of the branch lines to act as a sender in combinationsuccessively with each of the other branch lines then acting as areceiver, and while combining these various states with the variousconfigurations possible for the other branch lines that are actingneither as a sender nor as a receiver. Changeover from one configurationto another is controlled automatically by the computer programimplemented by the computer apparatus 32 whose instructions areconverted into electrical control signals by the converter 38.

With reference now to FIG. 3, there follows a description of a preferredembodiment of the first switch 26 enabling the "subscriber" cards to beconnected to the electrical signal generator 24, and also a preferredembodiment of a "subscriber" card 30. This switch has the structuredescribed above.

The switch 26 is essentially constituted by p lines of unit switchesgiven generic reference K. The first row of switches comprises two unitswitches K₁,1 and K₁,2 whose inputs are given generic reference a andare connected to respective output terminals 24b & 24c of the generator24. The outputs b and c of the unit switches K in the last row areconnected respectively to the positive external output terminals 40a ofthe switch assembly and to the negative terminals 40b of the switchassembly.

As also shown in FIG. 3, the switch includes a control unit 60 having asmany control outputs 62 as there are rows of unit switches, i.e. four inthe example under consideration. Each output 62 from the controlapparatus 60 serves to connect the a inputs of the unit switches in agiven row simultaneously to the b output terminals or simultaneously tothe c output terminals. A complete control instruction for the switch 26thus comprises four binary digits indicating whether the switches of acorresponding row i are to be in a position that connects the a inputsto the b terminals or in a position which connects the a inputs to the cterminals.

The electrical links between the output terminals b and c of the unitswitches K_(i) in row i and the terminals a of the switches K_(i+1) ofrow i+1 are such that the outputs 24b & 24c of the electrical generator24 can be connected to any one of the pairs of external output terminals40a & 40b of the switch 20, and to only one such pair. FIG. 2 shows onepossible configuration for the electrical connections.

In other words, when a control signal is applied to the input 26a of thecontrol apparatus 60 of the switch 26, the switches in the various rowstake up respective states enabling the generator 24 to be connected to aselected pair of external output terminals 40a & 40b, i.e. enabling thegenerator 24 to be connected to a determined "subscriber" card 30.

Still with reference to FIG. 2, a preferred embodiment of a "subscriber"card 30 is described. It has a first input/output pair constituted by apositive terminal 70a and a negative terminal 70b. As already mentioned,the terminals 70a & 70b are connected to a branch line 16 of the bus 10to be tested. The "subscriber" card includes a second pair of externalconnection terminals 72a & 72b for connection to a pair of externaloutput terminals 40a & 40b of the switch 26. The card 30 also has athird pair of external terminals 74a & 74b for connection to theexternal input terminals of the switch 28, as explained below.Double-pole switches 76 and 78 serve to connect the terminals 70a & 70brespectively to the terminals 72a & 72b and 74a & 74b, or on thecontrary to disconnect them therefrom. The terminals 70a & 70b can alsobe connected to a load 80 simulating the normal load which is to beapplied to the branch line in non-sending and non-receiving operation,which connection can be established by a switch 82, or else it cansimulate a short circuit which can be via conductor line 84 and a switch86. The "subscriber" card also includes a control circuit 88 whichenables the open or closed positions of the switches 76, 78, 82, and 86to be controlled individually depending on the state in which the branchline associated with the "subscriber" card is to be placed. In otherwords, the control circuit 88 receives a series of instructions via thecontrol input of the card 30a to cause one of its switches to be closedwhile the other three remain open.

FIG. 4 shows a preferred embodiment of the switch 28. This has exactlythe same architecture as the switch 26. It should merely be understoodthat where there used to be external output terminals there are nowexternal input terminals 42a & 42b of the switch for connecting each"subscriber" card 30 to the electrical measuring device 22. Moreprecisely, as shown in FIG. 4, the terminals 74a & 74b of each"subscriber" card 30 are connected to the external input terminals 42a &42b of the switch 28. The switch is controlled in rows by its controlcircuit 90 which receives instructions on an input 28a.

I claim:
 1. A switching assembly comprising:two external terminalsadapted and arranged to receive or provide an electronic signaltherebetween; p rows of switches, row i having 2^(i) switches, eachswitch having an input terminal, first and second output terminals, andcontrollable electrical connection means for selectively coupling saidinput terminal to said first output terminal or to said second outputterminal, each of said first and second output terminals of switches inrow i being electrically coupled to the input terminal of a respectiveswitch in row i+1, the two external terminals being coupled torespective input terminals of a pair of switches of the first row; andcontrol means for controlling the controllable electrical connectionmeans of all of the switches in the same row simultaneously in such amanner that for all of the switches of the same row, the input terminalis coupled to the first output terminal or is coupled to the secondoutput terminal depending on binary control states; each of the 2^(P)first output terminals and each of the 2^(P) second output terminalsbeing coupled to a respective one of a plurality of switching input oroutput terminals, and the first and second output terminals of the ithrow being coupled to the input terminals of the switches of the (i+1)throw in such a manner that for each combination of binary control statesof the control means of the rows of switches, the two external terminalsof said switching assembly can be coupled to any one single pair of theplurality of switching input or output terminals.
 2. A switchingassembly according to claim 1, wherein the switches are double-poleswitches under the control of opto-couplers.
 3. A switching assemblyaccording to claim 1, wherein the two external terminals are adapted andarranged to interface interchangeably with circuitry external to theswitching assembly.
 4. A switching assembly according to claim 1,wherein each of the plurality of switching input or output terminals isadapted and arranged to interface interchangeably with circuitryexternal to the switching assembly.
 5. A switching assembly,comprising:a pair of external terminals adapted and arranged to receiveor provide an electronic signal therebetween; "p" rows of switches, row"i" having 2^(i) switches, each switch having, first and second outputterminals, and an input terminal selectively coupled to said firstoutput terminal or to said second output terminal, each of said firstand second output terminals of switches in row "i" being electricallycoupled to the input terminal of a respective switch in row i+1, thepair of external terminals being coupled to respective input terminalsof switches of the first row; and a switch control circuit configured tocontrol the switches in the same row simultaneously in such a mannerthat for all of the switches of the same row, the input terminal iscoupled to the first output terminal or is coupled to the second outputterminal depending on binary control states; each of the 2^(P) firstoutput terminals and each of the 2^(P) second output terminals beingcoupled to a respective one of a plurality of switching input or outputterminals, and the first and second output terminals of the ith rowbeing coupled to the input terminals of the switches of the (i+1)th rowin such a manner that for each combination of binary control states ofthe control means of the rows of switches, the pair of externalterminals of said switching assembly can be coupled to any one singlepair of the plurality of switching input or output terminals.
 6. Aswitching assembly according to claim 5, wherein each of the pluralityof switching input or output terminals is adapted and arranged tointerface interchangeably with circuitry external to the switchingassembly.